A method for recording by means of an inkjet printer, a typical method among various color recording methods, performs recording by generating ink droplets and depositing them onto various record-receiving materials (such as paper, film and cloth). This method has been rapidly prevailing lately and is expected to grow remarkably in the future because of such features as less noise generation due to no contact of a recording head with a record-receiving material and easiness in downsizing and speedup. Conventionally, as an ink for a fountain pen or a felt pen and an ink for inkjet recording, a water-based ink dissolving a water-soluble dye in an aqueous medium has been used, and in these water-based inks, a water-soluble organic solvent is generally added to prevent ink from clogging at a pen tip or an inkjet nozzle. For this reason, these conventional inks are required to provide a recorded image of sufficient density, not to clog at a pen tip or an inkjet nozzle, to dry quickly on a record-receiving material, to bleed less, and to have good storage stability, and also water-soluble dye to be used is required, in particular, to have high solubility in water and a water-soluble organic solvent to be added to the inks. Moreover, an image formed is required to have image fastness such as water fastness, light fastness, ozone gas fastness and moisture fastness.
Ozone gas fastness means durability against phenomenon that ozone gas having oxidizing property in the air reacts with a dye on a recording paper to incur discoloration or fading of a printed image. Although oxidizing gas having this kind of action includes NOx and SOx besides ozone gas, ozone gas is said to be a main causative substance to promote the phenomenon of discoloration or fading of an inkjet recorded image more strongly, among these oxidizing gases. For an ink-receiving layer provided at the surface of a photo quality inkjet paper, so as to dry the ink faster and decrease bleed in high quality image, porous white inorganic substance and the like are often used as materials. Discoloration or fading in color caused by ozone gas occurs noticeably on such recording papers.
As the phenomenon of discoloration or fading caused by oxidizing gas are characteristics of inkjet images, improvement of ozone gas fastness is one of the most important problems.
To extend application field of a printing method using ink in the future, an ink composition to be used for inkjet recording and a colored article thereby are strongly required to exhibit further improved light fastness, ozone gas fastness, moisture fastness and water fastness.
Among inks with various hues prepared from various dyes, a black ink is an important one used for both of mono color and full color images. A lot of dyes for a black ink have been proposed so far, but one fully meeting the requirements of the marketplace has not been provided yet. Many of coloring matters proposed are disazo coloring matters, having such problems that hues are too shallow (reddish black), a color rendering property (a property of hue changing depending on a light source) is increased, water fastness and moisture fastness are inferior, gas fastness is not sufficient, and the like. Similarly, a great number of azo metal-complex coloring matters proposed have also such problems that they contain metal ion and considerations about safety of human bodies and environments are not included sufficiently, ozone gas fastness is not sufficient, and the like. In order to make the hue deeper, studies on polyazo coloring matter with the conjugate system increased have been done, but there still remain such problems that their hue density is low, the storage stability of aqueous solution and ink is inferior because their water solubility is low, their ozone gas fastness is not sufficient, and the like.
As a compound (coloring matter) for black ink for inkjet improved on ozone gas fastness which has been becoming one of the most important problems recently, for example, one described in Patent Literature 1 can be cited. The ozone gas fastness of these compounds, however, doesn't meet the requirements of the marketplace sufficiently. Furthermore, as a coloring matter compound for black ink, a trisazo compound is described in Patent Literature 2 and 3, but doesn't meet the requirements of the marketplace sufficiently, especially requirements on ozone gas fastness.    Patent Literature 1: JP 2003-183545 A    Patent Literature 2 JP 62-109872 A    Patent Literature 3: JP 2003-201412 A